edfas.org ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 21 NO. 4 4 EDFAAO (2019) 4:4-12 1537-0755/$19.00 ©ASM International ® POST-FIB CLEANING OF TEM SPECIMENS FROM 14 NM AND OTHER FINFETS BY CONCENTRATED ARGON ION MILLING C.S. Bonifacio, 1 M.J. Campin, 1 K. McIlwrath, 2 and P.E. Fischione 1 1 E.A. Fischione Instruments Inc., Export, Pennsylvania 2 JEOL USA, Peabody, Massachusetts email@example.com INTRODUCTION Today’s semiconductor devices, specifically fin field- effect transistors (FinFETs), are highly complex due to their multigate transistors and 3D gate structure design. Advanced devices are at the 10 and 7 nm nodes and are currently in production.  At the 10 nm node, the source- drain channel or fins are 25% taller and 25%more closely spaced than those in 14 nm node technologies.  The industry predicts that the FinFET design will persist up to the 5 nm node;  beyond that, the gate-all-around FETs [3,4,5] in the form of vertical nanowire, stacked, and complementary FETs are being considered. These future FETs are more intricate and have smaller features, which will consequently make smaller defects have a larger im- pact and harder to find. Metrology and physical failure analysis are already challenging due to the high aspect ratio and complexity of the FinFET structure. To accurately measure the struc- ture of these devices, transmission electron microscopy (TEM) is indispensable due to the resolution it provides. TEM characterization is part of the workflow in semicon- ductor process development and integration, as well as failure analysis for critical dimension (CD) measurements. Therefore, TEM is crucial for the development and pro- duction of advanced semiconductor devices given the decreasing device size. Specimen thickness of 20 nmor less is required to char- acterize the 3D structures of the 14 nm node FinFET gate oxide in the TEM.  Consequently, fast and reproducible TEM specimen preparation is essential. TEM specimens are usually prepared using a focused ion beam (FIB) tool due to the site specificity and accuracy of specimen thinning and extraction that it provides. [7,8] However, Ga + milling causes artifacts such as surface amorphization (post-FIB Si specimens with amorphous layers measured Fig. 1 Inverted FIB preparation of a full stack deprocessed devicemodified by additional steps a, b, g, and h; a-b are before and after milling the topmetal layers; g-h are before and after milling part of the Si substrate with trimmings during bulk milling and subsequent carbon cap deposition. Scale bars represent 5 µm.
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